Gas distribution system

ABSTRACT

The present invention provides a gas distribution apparatus useful in semiconductor manufacturing. The gas distribution apparatus comprises a unitary member and a gas distribution network formed within the unitary member for uniformly delivering a gas into a process region. The gas distribution network is formed of an inlet passage extending upwardly through the upper surface of the unitary member for connecting to a gas source, a plurality of first passages converged at a junction and connected with the inlet passage at the junction, a plurality of second passages connected with the plurality of first passages, and a plurality of outlet passages connected with the plurality of second passages for delivering the gas into a processing region. The first passages extend radially and outwardly from the junction to the periphery surface of the unitary member, and the second passages are non-perpendicular to the first passages and extend outwardly from the first passages to the periphery surface. The outlet passages extend downwardly through the lower surface of the unitary member for delivering the gas into the processing region.

CROSS REFERENCES TO RELATED APPLICATIONS

This application claims the benefit of and priority to U.S. ProvisionalApplication No. 60/475,079 filed May 30, 2003, the disclosure of whichis hereby incorporated by reference in its entirety. This application isa continuation application of U.S. patent application Ser. No.10/854,869 filed on May 26, 2004.

FIELD OF THE INVENTION

The present invention relates generally to the field of semiconductorequipment and processing. More specifically, the present inventionrelates to a gas distribution apparatus useful in semiconductorfabrication.

BACKGROUND OF THE INVENTION

Wafer processing reactor systems and methods are widely used in themanufacture of semiconductors and integrated circuits. One particulartype of wafer processing system utilizes chemical vapor deposition (CVD)to deposit films or layers on the surface of a substrate as a step inthe manufacture of semiconductors and integrated circuits. In CVDprocesses that require multiple gases, the gases are generally combinedwithin a mixing chamber. The gaseous mixture is then coupled through aconduit to a distribution plate or showerhead, which contains aplurality of holes such that the gaseous mixture is evenly distributedinto a process region. As the gaseous mixture enters the process regionand is infused with energy such as being heated, a chemical reactionoccurs between the gases to form a film on a substrate proximate theprocessing region.

Although it is generally advantageous to mix gases prior to deliveryinto a process region to ensure that the gases are uniformly distributedinto the process region, gases tend to begin reacting within the mixingchamber. Consequently, deposition or etching of the mixing chamber,conduits and other chamber components may occur prior to the gaseousmixture reaching the process region. Additionally, reaction by-productsand deposits may accumulate in the chamber gas delivery components.

Some semiconductor processes require delivery of gases into a processregion in a sequential manner without premixing. For example, in anatomic layer deposition (ALD) process, which increasingly becomes analternative to CVD processes, each reactant gas is independentlyintroduced into a reaction chamber through, for example, a showerhead,so that no gas phase intermixing occurs. A monolayer of a first reactantis physi- or chemi-sorbed onto a substrate surface. After the excessfirst reactant is evacuated from the reaction chamber, a second reactantis then introduced through the showerhead to the reaction chamber andreacts with the first reactant to form a monolayer of the desired filmvia a self-limiting surface reaction. A desired film thickness isobtained by repeating the deposition cycle as necessary. It isadvantageous to introduce the first and second reactants independentlyand separately through the showerhead to avoid any reaction between thereactants in the showerhead.

Therefore, in either a CVD or an ALD process, it is desired to maintaingases in separate passageways within a showerhead until they exit theshowerhead into a process region.

To distribute process gases from a single inlet port to a multitude ofoutlet holes, gas distribution networks created in a showerhead body maybe used. For example, a plurality of parallel channels can be formed ina unitary showerhead body from which a multitude of perpendicular outletchannels deliver process chemicals into a process region. The parallelchannels are intersected perpendicularly by a single transverse plenumconnected to a central gas source inlet line. Process gas passes fromthe inlet to the outlets of the showerhead by following a “Cartesian”path by flowing laterally along the transverse plenum, transversethrough the parallel channels, and the outlet channels into the processregion.

A disadvantage of this design is that there is a large variation intotal flow path to reach points of constant radius within theshowerhead. As a result, there is typical a large variation inbackpressure within the interior flow channels that result in anunacceptable azimuthal and radial variation in outlet gas flow velocityfrom the multitude of outlet holes. Furthermore, in showerhead designswith a single central gas inlet, there exists an unavoidable time lagbetween the gases that exist near the center of the showerhead and thoseexisting at the outer perimeter. The large variation in total flow pathat points of constant radius inherent with Cartesian-style flow networkscreates a “phase error” that may lead to non-uniform chemicalconcentrations around the perimeter of the showerhead which may affectdeposition in transient-flow processes.

To minimize the azimuthal variation in time-lag, radially orientedchannels that converge at the center gas inlet may be employed insteadof a multitude of parallel channels. However, this type of design leadsto a decreasing outlet hole density (hole per square centimeter) due tothe divergence of the radial passages. This may be compensated somewhatby additional radial passages at larger radii, however, these requirecross-connection to the same source of gas which becomes difficult to doin a truly unit body block of material. Furthermore, it is not apparentthat this will yield acceptable flow uniformity either.

Therefore, there is a need of a gas distribution system that providesimproved uniform outlet velocity distribution and reduced variation inazimuthal time lag between the gases that exit near the center of theshowerhead and those existing at the outer perimeter. Furtherdevelopments in gas distribution apparatus useful in CVD and ALDprocesses are needed.

SUMMARY OF THE INVENTION

A gas distribution apparatus useful in semiconductor fabrication isprovided. The gas distribution apparatus promotes uniformly delivery ofgases into a process region and reduces azimuthal variation in time lagbetween gas that exits near the center and gas exiting at the outerperimeter of the apparatus.

In one embodiment, the present gas distribution apparatus comprises amember and a gas distribution network formed within the unitary memberfor uniformly delivering a gas into a process region. The member can bea unitary member. The gas distribution network is formed of an inletpassage extending upwardly through the upper surface of the unitarymember for connecting to a gas source. A plurality of first passagesconverge at a junction and interconnect with the inlet passage at thejunction. A plurality of second passages are connected with theplurality of first passages, and a plurality of outlet passages areconnected with the plurality of second passages for delivering the gasinto a processing region. The first passages extend radially andoutwardly from the junction to the periphery surface of the unitarymember. The second passages are non-perpendicular to the first passagesand extend outwardly from the first passages to the periphery surface.The outlet passages extend downwardly through the lower surface of theunitary member for delivering the gas into the processing region.

In one embodiment, the first passages are comprised of four orthogonalcoordinate passages dividing the gas distribution network into fourregions or quadrants. The second passages in each of the quadrants areparallel with each other. In opposite two quadrants, the first andsecond passages are symmetrically arranged. In adjacent two quadrants,the second passages on both sides of a common first passage arestaggeredly arranged. The first and second passages constitute an anglefrom about 30 to about 45. In one embodiment, the angle is about 45degrees.

In another embodiment, the first passages are comprised of six passages,and adjacent two passages form an angle of about 60 degrees.

Generally, the first passages have a diameter larger than the diameterof the second passages. The second passages have a diameter larger thanthe diameter of the outlet passages. In one embodiment, the diameter ofthe first passages is in the range from about 5 to about 15 mm, thediameter of the second passages is in the range from about 3 to about 12mm, and the outlet diameter is in the range from about 0.25 to about 2.5mm.

In another embodiment, the outlet passages are substantially cylindricaland adapted to receive inserts to alter the size of and/or direction ofgases exiting the outlets into a process region. In a furtherembodiment, the outlet passages are provided with threads for receivingthe inserts.

In one embodiment, the present gas distribution system comprises aunitary cylindrical member and two independent gas distribution networksformed within the unitary member. Each of the gas distribution networksis formed of an inlet passage extending upwardly through the uppersurface of the unitary member for connecting to a gas source, aplurality of co-planar first passages converged at a junction andinterconnected with the inlet passage at the junction, a plurality ofsecond passages connected with the plurality of first passages, and aplurality of outlet passages connected with the plurality of secondpassages and extending downwardly through the lower surface of theunitary member for delivering the gas into the processing region. Thefirst passages extend radially and outwardly from the junction to theperiphery surface of the unitary member. The second passages areco-planar with and non-perpendicular to the first passages and extendoutwardly from the first passages to the periphery surface. The firstand second passages of each of the gas distribution networks are formedat different elevations within the unitary member and the inlet passagesof each of the gas distribution networks offset each other. The twoindependent gas distribution networks are not in fluid communicationwithin the unitary member. In one embodiment, the first passages of eachof the gas distribution networks are comprised of four orthogonalcoordinate passages. In another embodiment, the outlet passages of eachof the two gas distribution networks extend through the lower surface inan alternate and even configuration. In a further embodiment, the twogas distribution networks have substantially the same dimensions andconfigurations.

In one embedment, the present gas distribution system comprises aunitary cylindrical member having an upper surface, a lower surface anda periphery surface, and three independent gas distribution networksformed within the unitary member. Each of the gas distribution networksis formed of an inlet passage, a plurality of first passages, aplurality of second passages connected with the first passages, and aplurality of outlet passages connected with the second passages. Theinlet passage extends upwardly through the upper surface for connectingto a gas source. The first passages converge at a junction and isinterconnected with the inlet passage at the junction. The firstpassages extend radially and outwardly from the junction to theperiphery surface. The second passages are co-planar with andnon-perpendicular to the first passages and extend outwardly from thefirst passages to the periphery surface. The outlet passages areconnected with the second passages and extend downwardly through thelower surface for delivering the gas into the processing region. Thefirst and second passages of each of the three gas distribution networksare formed at different elevations within the unitary member and theinlet passages of each of the three gas distribution networks offseteach other. The three independent gas distribution networks are not influid communication within the unitary member. In one embodiment, thefirst passages of each of the three gas distribution networks arecomprised of six passages, and adjacent two passages form an angle ofabout 60 degrees. The three gas distribution networks may havesubstantially the same dimensions and configurations.

BRIEF DESCRIPTION OF THE DRAWINGS

Other objects and advantages of the present invention become apparentupon reading of the detailed description of the invention provided belowand upon reference to the drawings in which:

FIG. 1 is a schematic view of a semiconductor reactor system including agas distribution apparatus in accordance with one embodiment of thepresent invention.

FIG. 2 is an external view of a gas distribution apparatus machined froma unitary member in accordance with one embodiment of the presentinvention.

FIG. 3 shows an internal gas distribution network formed within aunitary member in accordance with one embodiment of the presentinvention.

FIG. 4 is an external view of a gas distribution apparatus showingoutlet passages through the bottom surface of a unitary member inaccordance with one embodiment of the invention.

FIG. 5 is a bubble plot showing outlet velocities in the geometry of aprior art showerhead.

FIG. 6 is a bubble plot showing outlet velocities in the geometry of agas distribution apparatus in accordance with one embodiment of thepresent invention.

FIG. 7 is a plot showing internal and external path length ratios in aprior art showerhead.

FIG. 8 is a plot showing internal and external path length ratios in agas distribution apparatus in accordance with one embodiment of thepresent invention.

FIG. 9 shows two internal gas distribution networks formed within aunitary member in accordance with one embodiment of the presentinvention.

DETAILED DESCRIPTION OF THE INVENTION

A gas distribution apparatus useful in semiconductor fabrication isprovided. In general, the gas distribution apparatus of the presentinvention comprises a unitary member and one or more gas distributionnetworks formed within the unitary member for uniformly delivering gasesinto a process region.

Referring to the drawings where like components are designated by likereference numerals, the present gas distribution apparatus is describedin more detail.

FIG. 1 schematically shows a semiconductor wafer processing reactionchamber 10, for example, an atomic layer deposition (ALD) reactor or aCVD reactor that includes a showerhead 12 of the present invention. Itshould be noted that the reactor 10 shown in FIG. 1 is for illustrativepurpose only and not intended to limit the scope of the invention in anyway. The showerhead described below can be used in any other systemwhere uniform gas distribution into a process region is desired. Thereactor 10 includes an enclosure 14 defining a processing region 16. Asubstrate 18, such as a semiconductor wafer, is maintained proximate theprocess region 16 on a pedestal 20. The pedestal 20 moves verticallywithin the enclosure 14 to a position that allows the substrate 18 to beremoved. While in the lowered position, a new substrate 18 is placed onthe pedestal 20. The pedestal 20 is then raised into a process position,which places the substrate proximate the process region 16. Processgases are supplied through the showerhead 12. The showerhead 12 forms alid of the reactor 10. In one embodiment of the present invention, forexample, in a CVD process, two gases (Gas 1 and 2) are independently andseparately supplied to the showerhead 12. The two gases are distributedto the process region 16 via two separate gas distribution networks 21formed in the showerhead 12. These gases react and form a deposit on thesubstrate 18. In another embodiment of the present invention, forexample, in an ALD process, a first reactant gas (Gas 1) is introducedinto the process region 16 via a gas distribution network formed withinthe showerhead 12. After a monolayer of a first reactant gas is physi-or chemi-sorbed onto the substrate surface, the excess first reactantgas is evacuated from the reaction chamber 10 with the aid of an inertpurge gas. A second reactant (Gas 2) is then introduced to the processregion 16 via a separate gas distribution network formed within theshowerhead. The second reactant gas reacts with the first reactantforming a monolayer of the desired film via a self-limiting surfacereaction. The excess second reactant is then evacuated with the aid ofan inert purge gas. A desired film thickness is obtained by repeatingthe deposition cycle as necessary.

The showerhead 12 is preferably a unitary member 13, as shown in FIG. 2,and has one or more gas distribution networks 21, as shown in FIG. 3,formed within the unitary member 13. Member 13 can also be two or moreblocks combined together. To simplify description of the invention, asingle gas port 22 and a single gas distribution network 21 are shown inFIGS. 2 and 3. It should be noted that two or three gas distributionnetworks 21 can be independently formed at different elevations withinthe unitary member 13, and two or three gas ports 22 can be provided toindependently and separately supply gases into the two or three gasdistribution networks 21. The two or three gas distribution networks 21are not interconnected within the unitary member 13 so that two or threegases are independently and separately introduced into a process region16 without premixing. In one embodiment where two or three gasdistribution networks 21 are formed within the unitary member 13, two orthree gases can be simultaneously supplied into the showerhead 12 fromseparate gas sources (not shown). Since the two or three gasdistribution networks 21 are not in fluid communication with each otherwithin the unitary member 13, the two or three gases are not mixed untilthey exit the showerhead 12 into the process region 16. Alternatively,two or three gases are supplied into the process region 16 sequentiallyvia the two or three gas distribution networks 21 within the unitarymember 13 to meet specific process requirements, for example, in anatomic layer deposition process.

Member 13 is preferably machined from a block of aluminum, stainlesssteel, nickel-based alloys, or any material that does not react with theparticular gases being supplied into the showerhead 12. The unitarymember 13 can be in a cylindrical shape or any shape suitable as a lidfor the reactor 10. The unitary member 13 comprises an upper surface 23,a lower surface 24, and a peripheral surface 25. A plurality ofchannels, passages or holes are formed within the unitary member 13 toform a gas distribution network 21. Various manufacturing techniquesknown in the art can be used to form the channels, passages or holes,such as electric discharge drilling, mechanical drilling, pressurizedreactant drilling, water jet cutting, and the like. In one embodiment,these channels or passages are formed by mechanical drilling and/or anelectrode discharge machine (EDM).

FIG. 3 shows a gas distribution network 21 formed within the unitarymember 13. For clarity, only channels, passages, or holes forming thegas distribution network 21 are shown in FIG. 3. The remaining solidmaterials that define these channels, passages or holes of the gasdistribution network 21 are not shown in FIG. 3.

As illustrated in FIG. 3, the gas distribution network 21 comprises aninlet passage 26. The inlet passage 26 is coupled to a gas source (notshown) via a conduit (not shown) for supplying a gas into the gasdistribution network 21. The inlet 26 extends upwardly and through theupper surface 23.

A plurality of horizontal passages or plenums 28 a-d are formed withinthe unitary member 13. The horizontal plenums 28 a-d are converged at ajunction 30 and extend radially and outwardly to the peripheral surface25 of the unitary member 13. The horizontal plenums 28 a-d are closed atthe peripheral surface 25. The horizontal plenums 28 a-d can be formedby drilling from the peripheral surface 25. The openings on theperipheral surface 25 are closed by for example sealing plugs (notshown) after the plenums 28 a-d are formed. The inlet passage 26 isconnected with the plenums 28 a-d via the junction 30. In FIG. 3, fourorthogonal coordinate plenums 28 a-d are shown for illustrative purpose.It should be noted that other number of plenums can be formed. Forexample, six plenums can be formed converging at a junction, andadjacent two plenums constitute an angle of 60 degrees. A gas isintroduced via the inlet passage 26 and distributed into the horizontalplenums 28 a-d.

A plurality of branch passages or tributaries 32 are formed along thepath of each of the horizontal plenums 28 a-d. The tributaries 32 extendfrom the plenum 28 to the peripheral surface 25 of the unitary member13. The tributaries 32 are closed at the peripheral surface 25. Thesebranch passages or tributaries 32 are formed at a same elevation withthe plenums 28. In one embodiment, such as shown in FIG. 3, the gasdistribution network 21 is divided into four regions or quadrants 34 a-dby four orthogonal coordinate plenums 28 a-d. An array of paralleltributaries 32 are formed in each of the quadrants 34 a-d. The length ofeach of individual tributary 32 is determined to define a desired gasdistribution configuration. In one embodiment where a substantiallycircular distribution configuration is desired, each individualtributary 32 extends outwardly and closed at a location that issubstantially equally distant from the peripheral surface 25 of thecylindrical member 13. Other distribution configurations such as asquare pattern can be defined by varying the length of the plenums 28a-d, tributaries 32, and outlets 36 described below.

In opposite two quadrants such as 34 a and 34 c, or 34 b and 34 d, theconfiguration of tributaries 32 are symmetrical. In adjacent twoquadrants such as 34 a and 34 b, or 34 a and 34 c, the tributaries 32formed along a common plenum such as 28 a or 28 b are staggered andangled from the plenum. In one embodiment, each tributary 32 forms anacute angle with the plenum 28 of about 45 degrees. This angle can bedetermined by the geometrical requirements imposed by the number of gasdistribution networks and the desired outlet hole patterns.

Along the path of each of the tributaries 32, an array of passages oroutlets 36 are formed for distributing gases into a process region 16.The outlets 36 extends downwardly and through the lower surface 24 ofthe unitary member 13 as shown in FIG. 4. The passages of the outlets 36can be straight and cylindrical. Alternatively, the passages of theoutlets 36 comprise a first portion proximate the tributary 32 and asecond portion distant the tributary 32. The first portion of the outletpassage may have a larger or smaller diameter than that of the secondportion to control the back pressure of the outlets 36 according toprocess requirements. The outlet passages may also be provided withthreads for receiving inserts that are designed to alter the size of theoutlet or direction of gases exiting the outlet into the process region.U.S. application Ser. No. ______ (Attorney Docket No. A-72314) entitled“Adjustable Gas Distribution System” filed concurrently with thisapplication discloses embodiments of inserts that can be used in thepresent gas distribution system, the disclosure of which is herebyincorporated by reference in its entirety.

The diameters of the plenums 28 a-d, tributaries 32, and outlets 36 areselected to provide a desired outlet velocity. In one embodiment, thediameters of the plenums 28 a-d are larger than those of the tributaries32, and the diameters of the tributaries 32 are larger than those of theoutlets 36. Small outlet diameters create resistance to gas flow so asto sustain smaller variation in back pressure among all of the outlets.Large plenum and tributary diameters assist in this effect which isdesirable. Typically, if the backing pressure is uniform among all theoutlets, the outlet velocities are also uniform. However, it isdesirable not to make the outlets too small as this may lead to“jetting” of gases, which is undesirable in semiconductor processes. Thediameters of the outlets 36 can be uniform throughout the entiredistribution region. Alternatively, the diameters of the outlets 32differ to provide an inner region with a larger diameters and an outerregion with smaller diameters.

In one embodiment, the diameter of the plenums 28 a-d is selected in therange from about 5 mm to about 15 mm, the diameter of the tributaries 32in the range from about 3 mm to about 12 mm, and the diameter of theoutlets 36 in the range from about 0.25 mm to about 2.5 mm. In anotherembodiment, the diameter of the plenums 28 a-d is selected in the rangefrom about 9 mm to about 12 mm, the diameter of the tributaries 32 inthe range from about 6 mm to about 9 mm, and the diameter of the outlets36 in the range from about 1 mm to about 1.5 mm.

For clarity and simplicity, only some tributaries, outlets and plenumsare shown in FIG. 3 for illustrative purpose. It should be noted thatnumerous tributaries and outlets can be formed to provide desired outletdensity for specific processes. For example, the number of plenums,tributaries and outlets are selected to provide an outlet density ofabout 1 hole per 2 square centimeters.

Table 1 summarizes the modeling results for the present gas distributionsystem as analyzed in computational fluid dynamics (CFD) simulations.TABLE 1 Plenum Tributary Outlet Diameter Diameter Diameter Range/ Max/Design No. (mm) (mm) (mm) Average Min 1 10.0 8.0 1.5 0.131 1.138 2 10.08.0 1.5 0.133 1.140 3 8.0 8.0 1.5 0.203 1.220 4 9.0 6.0 1.5 0.268 1.2875 8.0 8.0 1.5 0.290 1.328 6 10.0 6.0 1.5 0.337 1.364

In Table 1, Max/Min refers to the ratio of maximum to minimum outletvelocity. Range/Average refers to the ratio of Max/Min value to theaverage gas flow velocity. The values of Max/Min and Range/Average areused to rank the performance of the gas distribution systems. Smallvalues of Max/Min and Range/Average are desired for uniform distributionof gases into a process region.

Table 1 demonstrates a much better performance of the present gasdistribution apparatus over prior art showerheads. In a prior artshowerhead of the Cartesian style network type, the Max/Min ratio wastested and found to be 3.584, which means that the variation of theoutlet velocity is as high as more than 350%, and the Range/Average was1.50, or 150%. In comparison, the Max/Min ratios for the gasdistribution system of the present invention range only from 1.220 to1.364, and the Range/Average ratios range only from 0.131 to 0.337.

FIG. 5 is a bubble plot that shows the outlet velocities in the geometryof a prior art showerhead. FIG. 6 is a bubble plot that shows the outletvelocities in the geometry of the present gas distribution system asdefined by design 5 in Table 1. As shown in FIG. 5, the bubbles in theouter perimeter regions are obviously smaller than those in the innerregion. In other words, the flow velocities in the inner region aregreater than those in the outer perimeter region. FIG. 6 shows animprovement of the flow velocity provided by the gas distribution systemof the present invention. FIG. 6 demonstrates a substantially uniformoutlet velocities regardless of the distance from the center region.

One advantage of the present gas distribution system is a smallertransit time variation in the polar directions over that of the priorart showerhead design. FIGS. 7 and 8 compare the internal and externalpath length in the present gas distribution system and prior artshowerhead. In FIGS. 7 and 8, x-axis represents outlet perimeterpositions, and y-axis represents the length ratio of an internal pathfor a gas traveling to an outlet at the outer parameter and an externalpath that the gas would travel from the center junction radially andoutwardly towards that same outlet. In the present gas distributionsystem illustrated in FIG. 3, the internal/external path ratio atperimeter positions G and H is close to 1 due to the radial design, asshown in FIG. 8. In a prior art showerhead, the internal/external pathratio at a equivalent perimeter positions can be as high as 1.4, asshown in FIG. 7. FIGS. 7 and 8 demonstrate that the present gasdistribution system greatly reduces the azimuthal variation in time lagbetween gases that exit near the center of the showerhead and thoseexiting at the outer perimeter. This in turn enhances gas distributionuniformity into a process region, which is desirable in semiconductormanufacturing.

In one embodiment, two internal gas distribution networks are formed atdifferent elevations within a unitary member to independently andseparately supply two gases into a process region. Each of the twointernal gas distribution networks is described above with reference toFIGS. 2-8. The two internal gas distribution networks are not in fluidcommunication within the unitary member. The configuration of the twointernal gas distribution networks can be substantially the same. In oneembodiment as shown in FIG. 9, each of the two internal gas distributionnetworks is divided into four regions or quadrants by four orthogonalcoordinate main passages or plenums 54 a-d and 64 a-d. The four plenumsconverge at a junction and extend radially and outwardly to theperipheral surface of the unitary member. A plurality of parallel branchpassages or tributaries 58 and 68 are formed in each of the quadrants.The tributaries 58 and 68 are coupled to the plenums 54 a-d and 64 a-drespectively and extend outwardly to the peripheral surface of theunitary member. The tributaries and the plenum connected therewithconstitute an angle about 45 degrees. An inlet passage is formed andcoupled to the junction of the plenums. The inlet passage extendsupwardly and through the upper surface of the unitary member to coupleto a gas source via a conduit. A plurality of vertical outlet passages59 and 69 are formed along the path of each of the tributaries 58 and 68respectively. The outlet passages 59 and 69 extend downwardly andthrough the lower surface of the unitary member for directing gases intoa process region.

The two internal gas distribution networks are arranged at differentelevations within the unitary member in such a manner so that theplenums, tributaries, inlet and outlet passages of one internal gasdistribution network offset corresponding plenums, tributaries, inletand outlet passages of another internal gas distribution network. Inother words, the corresponding plenums, tributaries, and inlet andoutlet passages are not overlapped when viewed from the top or bottom ofthe unitary member. When viewed from the bottom of the unitary member,the outlet passages of each of the internal gas distribution networksextend through the bottom surface in an alternative and evenconfiguration.

In a further embodiment, three internal gas distribution networks areformed at different elevations within a unitary member to independentlyand separately supply three gases into a process region. Each of thethree internal gas distribution networks is described above withreference to FIGS. 2-8. The three internal gas distribution networks arenot in fluid communication within the unitary member. The configurationof the three internal gas distribution networks can be substantially thesame. In one embodiment, each of the three internal gas distributionnetworks is divided into six regions by six main passages or plenums.The six plenums converge at a junction and extend radially and outwardlyto the peripheral surface of the unitary member. A plurality of parallelbranch passages or tributaries are formed in each of the six regions.The tributaries are coupled to the plenums and extend outwardly to theperipheral surface of the unitary member. The tributaries and the plenumconnected therewith constitute an angle about 30 degrees. An inletpassage is formed and coupled to the junction of the plenums. The inletpassage extends upwardly and through the upper surface of the unitarymember to couple to a gas source via a conduit. A plurality of verticaloutlet passages are formed along the path of each of the tributaries.The outlet passages extend downwardly and through the lower surface ofthe unitary member for directing gases into a process region.

The three internal gas distribution networks are arranged at differentelevations within the unitary member in such a manner so that the inletand outlet passages of one internal gas distribution network offset theinlet and outlet passages of the other two internal gas distributionnetwork. In other words, the corresponding inlet and out passages arenot overlapped when viewed from the top or bottom of the unitary member.

As described above, a gas distribution apparatus has been provided bythe present invention. The foregoing description of specific embodimentsof the invention have been presented for the purpose of illustration anddescription. They are not intended to be exhaustive or to limit theinvention to the precise forms disclosed, and obviously manymodifications, embodiments, and variations are possible in light of theabove teaching. It is intended that the scope of the invention bedefined by the claims appended hereto and their equivalents.

1. A gas distribution apparatus, comprising: a member having an uppersurface, a lower surface and a periphery surface; and a gas distributionnetwork formed within said member for uniformly delivering a gas into aprocess region, said gas distribution network being formed of: an inletpassage extending upwardly through said upper surface for connecting toa gas source; a plurality of first passages converged at a junction andconnected with said inlet passage at the junction, said first passagesextend radially and outwardly from the junction to the peripherysurface; a plurality of second passages connected with said plurality offirst passages, said second passages are non-perpendicular to said firstpassages and extend outwardly from said first passages to the peripherysurface; and a plurality of outlet passages connected with saidplurality of second passages and extending downwardly through said lowersurface for delivering the gas into the processing region.
 2. Theapparatus of claim 1 wherein said member is cylindrical unitary member.3. The apparatus of claim 1 wherein said plurality of first and secondpassages are co-planar.
 4. The apparatus of claim 1 wherein saidplurality of second passages between adjacent two passages are inparallel.
 5. The apparatus of claim 1 wherein said second passages areangled from the first passage connected therewith from about 30 to about45 degree.
 6. The apparatus of claim 5 wherein said second passages areangled from the first passage in about 45 degree.
 7. The apparatus ofclaim 1 wherein said second passages connected on both sides of a commonfirst passage are staggeredly arranged.
 8. The apparatus of claim 1wherein said first passages are comprised of four orthogonal coordinatepassages
 9. The apparatus of claim 1 wherein said first passages arecomprised of six passages, and adjacent two passages form an angle ofabout 60 degree.
 10. The apparatus of claim 1 wherein the first passageshave a first diameter, the second passages have a second diameter, andthe outlet passages have an outlet diameter, where the first diameter islarger than the second diameter, and the second diameter is larger thanthe outlet diameter.
 11. The apparatus of claim 10 wherein the firstdiameter is selected in the range from about 5 to about 15 mm, thesecond diameter in the range from about 3 to about 12 mm, and the outletdiameter in the range from about 0.25 to about 2.5 mm.
 12. The apparatusof claim 1 wherein the outlets have a substantially constant density onthe lower surface of the unitary member.
 13. The apparatus of claim 1wherein the outlet passages are substantially cylindrical.
 14. Theapparatus of claim 1 wherein the outlet passages are formed of a firstportion having a smaller diameter and a second portion having a greaterdiameter.
 15. The apparatus of claim 1 wherein the outlet passages isprovided with threading for receiving inserts to alter the size ofand/or the direction of the gas exiting the outlet passages.
 16. A gasdistribution apparatus comprising: a plurality of first passages; and aplurality of second passages coupled to said plurality of firstpassages; wherein the first passages are comprised of four quadrants,and where in two opposite quadrants the first and second passages aresymmetrically arranged and in two adjacent quadrants the second passageson both sides of a common first passage are staggeridly arranged.